Bituminous substances, such as asphalt, have poor fluidity, and can be burned only with difficulty. Furthermore, the bituminous substances have the disadvantage that when they are burned, the amount of free carbon formed by incomplete combustion is undesirably high, resulting in the formation of large amounts of soot and coke.
In order to overcome such undesirable properties of the bituminous substance, it is considered desirable to disperse water in the bituminous substance to accelerate the formation of fine bituminous substance particles, increase the combustion efficiency, and decrease the formation of soot and nitrogen oxides. This method, however, has several disadvantages. For example, the amount of water required for reducing the formation of soot and nitrogen oxides in accordance with such a method reaches from 5 to 20% by weight, based on the weight of the bituminous substances, and therefore the loss of heat into the steam being discharged is undesirably high. Furthermore, since the particle size of the dispersion composition is large and the dispersion is unstable, it is necessary to add emulsifiers.
U.S. Pat. No. 1,609,308 discloses a process for preparing an oil-in-water type dispersion composition in which asphalt and water are kneaded to allow the water to be absorbed in the asphalt, a dispersant such as colloidal clay is added thereto, and then water is gradually added thereto to cause the phase inversion (also referred to as phase reversal).
U.S. Pat. No. 2,247,722 and British Pat. No. 465,589 disclose a process for preparing an oil-in-water type dispersion composition in which tar, water and a water-soluble emulsifying agent are mixed to provide a water-in-oil type dispersion composition which is in turn added to and dispersed in an aqueous emulsifying agent solution to obtain the oil-in-water type dispersion composition.
U.S. Pat. No. 2,372,924 and British Pat. No. 506,300 disclose a process for preparing an oil-in-water type dispersion composition in which tar, water and an alkali-starch solution are mixed to provide a water-in-oil type dispersion composition which is in turn added to and dispersed in an alkali-starch solution and a large amount of an ammonia water to obtain the oil-in-water type dispersion composition.
However, neither the description suggesting the use of such oil-in-water type dispersion compositions as fuels, nor the description suggesting the incorporation of alcohols can be found.
Dispersion compositions composed of asphalt or tar and water, and containing no alcohol have poor stability and combustion properties, as illustrated in Comparative Examples 3 and 4 described hereinafter.
Japanese Patent Application (OPI) No. 160054/80 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") discloses a dispersion composition which is composed of a tar-like substance, an alcohol, and a dispersant, such as a partial saponification product of polyvinyl acetate. It has now been found, however, that although a part of the methanol is dissolved in the bituminous substance and the remainder is dispersed therein, the particle size of the dispersion composition is not uniform and the stability of the dispersion is poor. This indicates that such dispersion compositions composed of a tar-like substance and an alcohol, and containing no water have insufficient stability and are poor in the effect of reducing soot and nitrogen oxides as illustrated in Comparative Examples 1 and 2 as described hereinafter.
In addition, Japanese Patent Publication No. 4357/80 discloses a process for producing an emulsified fuel composed of a liquid hydrocarbon fuel, such as fuel oil and light oil, an alcohol, and water by the use of supersonic waves or a static mixer. There is, however, no disclosure concerning an emulsified fuel prepared using a bituminous substance, and also no disclosure concerning the preparation of dispersion compositions by kneading. In the use of a bituminous substance as a starting material, it is difficult to obtain the stable emulsified fuel by the supersonic waves or a static mixer.
These dispersions comprising bituminous substances and water or alcohols, therefore, are not suitable for practical use as fuels unless the stability of the dispersion and the economical efficiency are increased.
Japanese Patent Publication Nos. 31911/69 and 37675/78, and Japanese Patent Application Nos. 140974/79, 168961/79, 168962/79, 63001/80, 69343/80, and 131300/80 describe processes for producing dispersion compositions in which water-containing organic compounds such as peat and sludge, or aqueous organic compound-suspensions such as oil-containing waste water and emulsion waste water are kneaded with high viscoelastic substances such as atactic polypropylene and asphalt, to dehydrate the water-containing organic compound or aqueous organic compound-suspension and to allow the organic substance to be absorbed in the high viscoelastic substance. As one of the utilizations of the bituminous substance having an organic impurity absorbed thereto, the use as a fuel is considered. There is, however, no description concerning the incorporation of alcohols. Dispersion compositions containing no alcohol have poor stability and combustion properties.